4. 3 divisions of a cellstructure:
1. plasma membrane 2. cytoplasm 3. nucleus
A. PLASMA MEMBRANE
- boundary between theoutsideand insideenvironments
•selectively permeable/ semi-permeable
•regulates flow of materials intoand outof thecell
•also provides communication among and between cells and their
external environment
•made up of lipids andproteins
•fluidity – movement of bilayer; self-seals during injury;changes
position in the bilayer(but not flip-flopping); cholesterol
component provides strength at normal body temperature;
becomes fluid at low temperatures
5. PROKARYOTIC CELL
-A type of cell that lacks a membrane bounded nucleusand the DNA is not
physically separated from the rest of the cytoplasm. The DNA is usually
coiled, attached to the plasma membrane and concentrated in a region of
the cell called theNUCLEOID.
-Are usually very small (less than 5 u in length) with relatively simple
internal structureand are mostlysurrounded bya relativelystiff cell wall.
Ex. bacteria (KingdomMonera)
EUKARYOTIC CELL
-A Cell containing distinct membrane bounded nucleus aswell
as variety of membranous organelles that lend structural and
functional organization to the cellinterior
55. • Proteins are composed of amino acids – there are 20
different amino acids
• Different proteins are made by combining these 20
amino acids in different combinations
57. •Function of proteins:
1. Help fight disease
2. Build new body tissue
3. Enzymes used for digestion and other chemical
reactions are proteins
(Enzymes speed up the rate of a reaction)
4. Component of all cell membranes
59. Making a Protein—Transcription
• First Step: Copying of genetic information from DNA to RNA
called Transcription
Why? DNA has the genetic code for the protein that needs to be
made, but proteins are made by the ribosomes—ribosomes are
outside the nucleus in the cytoplasm.
DNA is too large to leave the nucleus (double stranded), but RNA
can leave the nucleus (single stranded).
60. • Part of DNA temporarily unzips and is used as a
template to assemble complementary nucleotides
into messenger RNA (mRNA).
61. • mRNA then goes through the pores of the nucleus with
the DNA code and attaches to the ribosome.
63. Making a Protein—Translation
• Second Step: Decoding of mRNA into a protein is called
Translation.
• Transfer RNA (tRNA) carries amino acids from the
cytoplasm to the ribosome.
64. These amino acids come from the food we eat. Proteins
we eat are broken down into individual amino acids and
then simply rearranged into new proteins according to the
needs and directions of our DNA.
65. •A series of three adjacent bases
in an mRNA molecule codes for
a specific amino acid—called a
codon.
•Each tRNA has 3 nucleotides
that are complementary to the
codon in mRNA.
•Each tRNA codes for a different
amino acid.
Amino acid
Anticodon
66. • mRNA carrying the DNA instructions and tRNA carrying
amino acids meet in the ribosomes.
67. • Amino acids are joined together to make a protein.
Polypeptide = Protein
68. Use one of the codon charts on the next page to find the amino acid
sequence coded for by the following mRNA strands.
CAC/CCA/UGG/UGA
___________/___________/___________/____________
AUG/AAC/GAC/UAA
___________/___________/___________/____________